Net Pulse Register

NPR-8

The SSI NPR-8 Net Pulse Register is a simplified pulse totalizer designed specifically for net energy metering applications. It accepts up to eight 2-Wire Form A input pulse sources, each assigned either a positive or negative sign, and tallies them into a net count register synchronized by an End-of-Interval (EOI) pulse. At the end of each interval, the net count is transferred to an output register and the accumulated pulses are delivered to downstream recording equipment at a selectable rate.

Typical applications include renewable energy installations — such as wind or solar PV systems — where generated energy must be netted against consumed energy before feeding a recorder, SCADA system, or electric meter pulse input. Setup is exceptionally straightforward: the only programmable parameters are pulse sign (positive or negative per channel) and output pulse width, both stored in non-volatile EEPROM memory.

The NPR-8 Net Pulse Register on a white background

Product Highlights

The NPR-8’s EOI-synchronized architecture ensures clean interval boundaries: at each EOI signal, the net count is latched into the output register and a new counting interval begins immediately. If the net count at interval end is zero or negative, no output pulses are generated — delivering only the true net positive energy to downstream devices. Output pulses are delivered at a selectable rate of 33mS, 67mS, or 100mS (default), and an Overflow LED indicates if the output register could not empty before the next EOI arrived.

Two isolated Form A dry-contact outputs are provided, both rated at 250VAC/VDC at 1/10A. Individual LEDs for each of the eight inputs and the EOI input provide immediate visual status, and an additional output LED flashes to confirm pulse delivery to the external device.

Features

The SSI NPR-8 totalized net pulse count from up to eight signed Form A inputs, synchronized by an EOI signal, with non-volatile memory and selectable output pulse rate.
  • Eight signed Form A inputs — each assignable positive or negative for net energy accumulation; two common K return terminals provided.
  • EOI-synchronized interval counting — net count is latched and output begins at each End-of-Interval pulse; new interval starts immediately.
  • Zero/negative suppression — no output pulses generated if net count is zero or negative at interval end.
  • Selectable output pulse rate — output speed configurable at 100mS (default), 67mS, or 33mS to match downstream equipment requirements.
  • Two isolated Form A outputs — dry KY contacts rated at 250VAC/VDC at 1/10A, with 2500Vrms input/output isolation.
  • Non-volatile EEPROM memory — stores count and output register values through power loss; all register values restored on power-up.
  • Per-input and output LED indicators — individual LEDs for all eight inputs, the EOI input, and the output provide complete real-time visual status.
The NPR-8 Net Pulse Register

Eight-Input Signed Net Register

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